Nickel electroplating electrolyte



United rates Patent flee 3,444,056 NICKEL ELECTRQPLATING ELECTROLYTE Carl Richter, chaifhausen, Switzerland, and Raymond Erdrnann, Saint-Maude, France, assignors to Cilag- Chemie, a corporation of Switzerland No Drawing. Filed June 24, 1966, Ser. No. 560,107 int. Cl. (32% /08, 5/46 U.S. Cl. 204-49 4 Claims ABSTRACT OF THE DISCLOURE An electrolyte for electrodepositing levelled and lustrous nickel comprising as additive either N-methyl-pyridine-3-sulfonic acid betaine or N-allyl-pyridine-3-sulfonic acid betaine.

This invention relates to the electro-deposition of levelled and lustrous nickel coatings, and, more particularly, to levelling and luster promoting agents to be used as additives in electrolytic nickel baths, and to novel electrolyte compositions containing such additives.

The addition of luster promoting agents to a conventional galvanic nickel bath is known in the art. However, while many organic compounds have been proposed as luster-promoting additives for electrolytic nickel baths, disadvantages still remain which have not been solved to the full satisfaction of the industry. For example, the use of unsaturated polyhydric alcohols, especially those containing a triple bond, have a tendency to form condensation products which unfavorably influence the luster formation. Other additives, although effective, are limited in use by their insuificient solubility or tendency to condense and polymerize, or they evaporate too easily.

It has now been found that lustrous and levelled nickel coatings having good mechanical properties may be obtained by the use of N-methyl-pyridine-3-sulfonic acid betaine or N-allylpyridine-S-sulfonic acid betaine, or a mixture of both, as an additive to galvanic nickel baths. In addition to promoting luster, these additives have the property of levelling the rough and uneven surface of metals.

The subject additives are advantageously employed in concentrations ranging from 0.1 gram per liter (g./l.) to saturation. With these additives, a strong, adherent and mirror smooth coating is obtained, and, contrary to many former luster promoting agents, an excess of these additives in the bath does not affect the deposition of a uniform coating. Furthermore, these additives are suitable for use in galvanic nickel baths either along or in combination with conventional luster-promoting additives, e.g., benzene sulfonates, naphthalene sulfonates, amido benzene sulfones, etc., and/or in conjunction With conventional Wetting agents such as the lauryl sulfates or with other ionized or non-ionized agents that decrease surface tension. The baths may also contain conventional bufiering agents such as, for example, boric acid, tartrates, etc.

The galvanic nickel bath comprises an aqueous acidic solution of a nickel salt, generally one selected from the group consisting of nickel sulfate, nickel sulfamate, nickel fluoborate, nickel chloride; nickel acetate may also be advantageously employed. Mixtures of such salts are also suitable. The pH value of the solution may vary from about 1.5 to about 6.0.

The compound, N-methyl-pyridine-3-sulfonic acid betaine, is known (see Beilstein, 22, 387, and US. Pat. No.

2,437,554). The N-alkyl compound, however, is not pre- 3,444,056 Patented May 13, 1969 viously described in the literature and its method of preparation is described below. The compounds may be structurally represented by the following formulas:

IL s 03 I SO CH3 ('JH -C H=CH2 N-methyl-pyridine-3 N-allyl-pyridine-3- sulfonic acid betaine sulfomc acid betaine The following examples are intended to illustrate, but not to limit, the scope of the present invention.

EXAMPLE I To a solution of 30.4 g. sodium hydroxide in 120 ml. water, 120 g. 3-pyridine sulfonic acid are added Wlth 190 g. ethanol and 57.6 g. allylchloride. This mixture is stirred for 3 hours at C. in a stainless steel auto-' clave. After allowing to cool, 100 ml. water is added and the whole solution is boiled with charcoal for about 10 minutes, followed by filtration. The clear solution is evaporated to dryness in vacuo. The residue is treated with 185 g. of methanol and 20 ml. water, then heated to reflux and filtered. The residue is now washed with 20 g. methanol. The filtrate is cooled to 5 C. and allowed to stand overnight. Then the precipitate is separated by filtration and Washed with g. methanol. After drying at 70 C. in vacuo, N-allyl-pyridine-3-sulfonic acid betaine is obtained, M.P. 172-176 C.

EXAMPLE II The following illustrate electrolytic baths according to the invention:

Nickel sulfate g./l 250 Nickel chloride do 40 Boric acid do 40 Luster-promoting agent 1 do.. 0.4 Sodium lauryl sulfate do 0.5 pH 4.6 Temperature C 20-60 Current density ....amp/dm. 1-7

Nickel sulfate g./l 280 Nickel chloride do 30 Boric acid do 45 Luster-promoting agent 1 do 0.6 Sodium lauryl sulfate do 0.8 pH 4.6 Temperature C 20-60 Current density amp/dm. 1-8

Nickel sulfamate g./l 300 Nickel chloride do 30 Boric acid do.. 40 Sodium lauryl sulfate do 0.1-0.4 N-methy1-pyridine-3-sulfonic acid betaine do 0.6-5.0 pH 2.3-5.8 Temperature C 25-50 Current density amp/dm. 1-7

See footnotes at end. of table.

Nickel chloride g./l 300 Nickel fluoborate do 40 Nickel acetate do 40 Sodium lauryl sulfate do 0.1-0.5 N-ally1-pyridine-3-sulfonic acid betaine pH 155.2 Temperature C 30-60 Current density amp/dm. 1-10 The levelling and luster promoting agent in these formulations can be either Nmethyl-pyridine-3-sulfonic acid betaine or N-allyl-pyridine-3-sulfonic acid betaine.

Enough for saturated solution (approximately 60 g./1.).

What is claimed is:

1. In a bath for electro-depositing levelled and lustrous nickel and comprising an aqueous acidic solution of at least one nickel salt, the improvement wherein said bath comprises the additive N-methyl-pyridine-3-sulfonic acid betaine in a concentration of 0.1 gram per liter to saturation.

2. The bath of claim 1 wherein said nickel salt is a member selected irom the group consisting of nickel sulfate, nickel chloride, nickel fiuoborate, nickel sulfamate and nickel acetate.

3. In a bath for electro-depositing levelled and lustrous nickel and comprising an aqueous acidic solution of at least one nickel salt, the improvement wherein said bath comprises the additive N-allyl-pyridine-3-sulfonic acid betaine in a concentration of 0.1 gram per liter to saturation.

4. The bath of claim 3 wherein said nickel salt is a member selected from the group consisting of nickel sulfate, nickel chloride, nickel fluoborate, nickel sulfamate and nickel acetate.

References Cited UNITED STATES PATENTS 2,876,177 3/1959 Giindel et al. 20449 3,006,822 10/1961 Todt 204-49 3,280,130 10/1966 Giindel 204-49 XR 3,314,868 4/1967 Willmund et al. 204-49 3,336,324 8/1967 Richter et a1 204-49 XR JOHN H. MACK, Primary Examiner.

G. L. KAPLAN, Assistant Examiner.

mg UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. qjml o g Dated My 11 1969 1 Carl Richter and Raymond Erdmann It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below In Column 1, line 72, the word "alkyl" should read allyl as corrected in the Examiner s amendment of October 11, 1968.

SIGNED AND SEALED GET 2 1 1969 (SEAL) Attest:

WILLIAM E. SCIHUYLER, JR.

Edward M. Fletcher, Jr,

Commissioner of Patents Attesting Officer 

